If you loved Overlord: The Dark Hero, try One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends
A bridge between a film you've already seen and one most people haven't. Here's what they share, and what the second one does that the first one doesn't.
You already loved

Overlord: The Dark Hero
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One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends
What they share
Both films are directed by Naoyuki Ito, and they both carry the playful mood tag, and they sit in Action / Adventure / Animation / Fantasy territory. If that's the register that drew you to Overlord: The Dark Hero, the second film will land in a comparable space — through a different lens.
playful
What One Piece "3D2Y": Overcome Ace's Death! Luffy's Vow to his Friends is
Here's a film that apparently fills in a gap. Luffy trains, but his routine gets disrupted when pirate Byrnndi World kidnaps Hancock's sisters. Luffy and Hancock then team up to save them from the World Government's hostage situation. It probably did well with its target audience.